this is bbc world news. the headlines... the us democratic presidential contender, joe biden, has accused donald trump of an overwhelming abuse of power. it follows reports he tried to pressure ukraine into opening a corruption investigation against mr biden and his son. saudi arabia has said that iran bears responsibility for the drone and missile strikes on its oil facilities last week. the saudi foreign minister said the attack used iranian weapons. teenage climate activist greta thunberg has arrived to cheering crowds at a youth summit on climate change in new york ahead of the un general assembly next week. thousands of paratroopers have taken part in a re—enactment of one of the key european battles of the second world war. they descended by parachute upon the dutch city of arnhem.

at 10pm kate silverton will have a full round—up of the day's news. first, time for our world — which this week focuses on twin girls who were born joined at the head then brought from pakistan to london's great ormond street children's hospital for a series of highly complex operations. safa and marwa are identical twins joined at the head. their family, from pakistan, want doctors to separate them. great ormond street in london is one of the few hospitals in the world with the expertise to do it. this is safa's brain, that's marwa's brain. what we need to achieve is effectively untwist the brains, and that is difficult, pretty difficult to do just in your head. but it is perilous. the bbc was given unique access to chart the complex medical

and ethical choices made... this is the day, the moment of truth, and everything hasjust got to be perfect. ..in the hope of giving the girls independent lives. safa and marwa are 21 months old, and were born in pakistan. they have come to london's great ormond street hospital with their mother zainab, grandfather and uncle, and are under the care of neurosurgeon owasejeelani. it is clearly very difficult to go through life when you are joined together like that, so it does make a very persuasive case in favour of doing the surgery. the family are very clear on that. clearly, life being separate is very much better than life together. if we felt there was not a very, very high chance that we could do it safely, we would be thinking

about whether we should do it or not. i think the whole team feel that there is an excellent chance of a successful separation here. the twins' father died just before they were born, and then it took more than a year of fundraising before a donor stepped in to cover the medical costs. safa and marwa are what's known as craniopagus twins, which meansjoined at the head. their skull is one long tube. the twins share many key blood vessels. separating these will be a major challenge. both twins' brains have a distorted appearance. one half is pointing up

into the other girl's skull cavity. every last detail of the twins' extraordinary anatomy has been recreated digitally. plastic surgeon david dunaway will be in charge of rebuilding the girls‘ skulls after neurosurgeon owasejeelani has separated the twins' brains. they showed me how 3d modelling has helped them to prepare. this hemisphere, which is the right hemisphere of the brain, is standing up, so this is actually projecting into the other child's skull. what we need to achieve is to effectively untwist the brains, and that's difficult, pretty difficult to do just in your head. for surgeons it is massively helpful, actually being able to touch and hold things makes so much difference to understanding how things are. we spent a long time looking at these models and going through the what—ifs. numerous models of the twins' brains and shared skull had been created

using this 3d printer. the whole process takes two days. this one will help surgeons plan how best to divide the layer of skin on the girls‘ skull once they are separated. and they're not only using physical models. this is surgery without scalpels. absolutely incredible. this is exactly what we wanted. virtual reality has helped the team plan how to divide the twins' shared arteries and veins. it works, it really works. and so now we can see a whole lot more information, a level of detail we've not been able to access previously. this is clearly the way of the future. we're using this technology for a highly complex case, but many other routine operations that we do, brain tumours, blood malformations,

so on and so forth, the rest of those malformations, this would be hugely, hugely beneficial for those cases as well. 0k, have we got everyone here? yeah? so we have one case for the list today, safa and marwa, two kids, one case. the surgery is so complex it will happen in three stages over several months. and the twins won't be physically separate until the final operation. the aim of the first

operation is to separate the twins' shared arteries. at present, each child is supplying the other‘s brain with blood. one, two, and three. what we're doing now is, the two arteries that are going from one twin to the other, so we can see the artery but to do anything to it we'll use the microscope. so the artery from safa going to supply marwa's brain has been clamped. but every time this is done, there's a risk of brain damage. ok, so the brain's looking good. the twins have been in theatre now for more than seven hours. and there are still several hours

of this operation to go. so far, everything is going to plan, and both girls are doing well. while one team works on the twins, another, led by david dunaway, constructs a frame made from pieces of the girls‘ skull which can be detached in subsequent operations. this central segment will be our rigid keel to hold the head together. what we need to do is make sure that the twins are rigidly together. being older, they‘re pretty active, and so whatever we do really has to be strong enough to resist the twisting and bending forces that they‘ll be putting on their heads. the first operation lasts 15 hours.

zainab has seven more children back in pakistan, aged 5—16. all of them were born at home, but with this pregnancy she was advised to deliver in hospital. it was not until five days after delivery by cesarean section that zainab was introduced to her daughters, initially by photo. zainab says the twins have distinct personalities.

after a month, the twins are back in theatre. this is safa‘s brain, it looks happy... this time the surgeons will separate the shared network of veins that drain blood from twin‘s brain. but disturbing this equilibrium could also do permanent damage. a portion of each twin‘s brain is being supplied by the other twin. so there is a real risk of causing a stroke at the time of the surgery, that is something that is weighing heavily on us. there could be something down there that i can‘t see at the moment. the more the surgeons try to divide the vessels that link and nourish them, the more unstable the twins become. we're going to have to take ventilation down.

0k? down? marwa‘s heart begins to fail. we are not stable, but we are less unstable. good enough for me. the anaesthetists manage to stabilise the girls so the operation can continue. because marwa is clearly the weaker twin, the surgeons decide to give her a key shared vein. the operation lasts 20 hours. so i‘m relieved, i‘m relieved. i mean there was a chance we were going to... potentially lose marwa during the surgery. it‘s been a big operation, but hopefully if they wake up as we hope they will, it‘s gone well. yeah.

but shortly after surgery, safa suffers a stroke. there was a period on tuesday evening where...we felt that we were very close to losing safa, and that she stayed in that critical state for... ..for 48—72 hours after the surgery. it was a very difficult time for the girls, their families and the entire team looking after them. in a break from their work at great ormond street, the two lead surgeons are in ireland to meet another set of twins.

it‘s eight years since they last saw ritaj and rital. it‘s hard to believe that these sisters, born in sudan, were once joined at the head. thank you! you are very welcome. back then the surgeons feared the girls might die unless separated. and this was rital and ritaj just one month after surgery. each parent able to hold a child in their arms. i hope that they will get a normal life and be treated as normal human beings. their father is now a doctor in ireland. we are now sitting here with two healthy twins, just like what i hoped at that time. so it‘s a great moment in my life as well. so the dream came true? exactly, yeah. i‘m a very proud dad now.

that was a very hard time. and at the same time it was a happy time because of the conclusion. rital has some learning difficulties. but the long—term outcome of the twins‘ separation has been hailed as a major success. the surgeons believe it‘s because it was done in the first year of life. what we put the two kids through and the brains through is a lot. and the younger brains and the younger circulations are better adapted. everything is easier. a one—year—old's regenerative capacities are so much better. the skin heals better, it stretches better, the bone grows in better. they‘re setting up a charity so that funds are available to pay for early intervention in future cases and for research into the best way to separate conjoined twins.

it‘s january 2019. i think the last two months after their last operation on the brain has been a little bit of a stormy time for safa and marwa. they‘ve had ups and downs with infections and temperatures and marwa‘s heart is having work quite hard for both of them and that‘s causing her a few challenges. but they‘re hanging in there. and they‘re both reasonably well. the next challenge for the surgeons is to ensure each twin will have enough skin to cover their skull when they‘re eventually separated. they do this by encouraging the skin to expand. the tissue expanders are balloons that sit underneath the skin and they have a tiny little port attached to them through which we can inject saline. so the idea now is that we will

gradually inject the tissue expanders and they will blow up like a balloon and the skin over the top of them will stretch. and it‘s a very, very effective technique of making more skin out of the skin we have available so that when we come to separate safa and marwa there‘s enough skin to cover both of their heads. these are rare cases leave a lasting impact on the surgeons. if i may, i haven‘t asked david‘s permission to say this. but the last separation that we did, when the kids were finally separated, and everyone was overjoyed and so on and so forth, and people were happy, and i looked at david and he had tears in his eyes. and he denies it to this day, but he did at that time. yeah. ithink... everybody has been so invested in this for so long. it is a surprisingly emotional thing, i think,

when they finally come apart. and when that experience of them actually leaving the operating theatre as two separate people is quite indescribable. at last, four months since the first surgery, the day of separation. two forceps. all laid out. so this is safa‘s brain that‘s marwa‘s brain. if you do give me a seven. little by little, the bone and the tissue which joins them is cut. so they are separate apart from that piece ofjewellery.

and then, after seven hours, the final connection is severed. fantastic. 0k. done. it's in a very emotional moment. we've been working a long time to get them here. they've been through so many operations and now it's worked. you still have four, five hours to do? yeah, we have to put them together now. so we've taken them apart and now we have to reconstruct their heads. marwa is still in the operating theatre through here, while safa has been moved just next door. for the first time, the survival of each of the twins is not dependent on the other. and that‘ll make it easier for the two surgical teams

to regulate their heart rate, blood pressure, and other vital signs. safa and marwa‘s brains used to have a distorted shape. but four months ago a plastic sheet was inserted between them and by gradually tightening the pressure it has largely corrected their appearance, essential before their skulls can be rebuilt. this means both teams can begin reconstruction. the patchwork of skull pieces are shared between theatres. so a piece for me, a piece for you. to have enough to cover their heads, each fragment must be divided in two. the skull is very usefully designed in three layers. so there is an inner layer of very thick, tough bone, an outer layer of thick, tough bone, and in between it the bone is like a honeycomb, so you can split the bone, it‘s half the thickness, but it means we should be able

to cover nearly all of the head with bone afterwards. this shows the jigsaw of bone fragments that were pieced together to form the skull of marwa on the left and safa on the right. the gaps have been seeded with bone cells. and in the months to come these should slowly close up. the final task of the 17—hour operation is to stretch the skin over their reconstructed skulls. it‘s a pretty amazing day, isn‘t it? everything is good. thank you. oh, what a day.

they have been quite amazing throughout, actually. they‘re a great family and i think they draw strength from one another. and they seem to be getting through it very well. we asked mum who she would pick up first, whether it was safa or marwa? and the answer was both — with support! so, ah, yeah... the road to recovery for the twins is slow, but four months after separation, safa and marwa are beginning to make progress. # hello, safa. # hello, marwa. # how are you today? the twins have daily physiotherapy. it‘s hoped this will help them reach some basic milestones — learning to roll, sit, and hold their heads up. # twinkle, twinkle, little star.

# how i wonder what you are... safa has not fully recovered from her stroke. we made the decision that the bulk of the common vessels go to marwa, the weaker twin. and because of the decision safa suffered a stroke. so what i really want to see is the weakness safa has at the moment, and she has a weakness in her left arm and left leg, improves. so for me the big moment‘s going to be when she walks and when she uses her left arm properly. because, you know, i have given her that weakness and for me that‘s a hard thing. nearly a year since they were admitted to hospital, the girls are leaving great ormond street.

the family will stay in london until the twins are strong enough to return to pakistan. the donor who paid for the surgery is continuing to support them. they are clearly going to face some challenges. but i think, overall, it‘s a positive outcome for them. they are going to need support, but they have a chance of leading a happy life. whatever hurdles safa and marwa may face in years to come, they will at least do that as a separate, independent girls. twins still, but conjoined no more.

temperatures on saturday reached into the high 20s in some spots with plenty of blue sky as well. for the change on the cards for the week ahead, it looks like that could be the last time we see temperatures getting that high until next spring oi’ summer. getting that high until next spring orsummer. ora getting that high until next spring oi’ summer. oi’ a more getting that high until next spring orsummer. ora more autumnalfeel to the weather in the week ahead with low pressure dominating and weather fronts working from the west. we have a cold front into sunday bringing heavy and persistent rain and gradually north and east with perhaps a rumble of thunder. ahead of that there will be showers pushing north and east and some could be sharp, bright skies feeding in behind to the south and west but still a chance of showers and temperatures town where they were on

saturday, the high teens and 20s for most and perhaps 23 for eastern england. for monday, that cold front works north and east with the brief dry interlude before the next weather front pushes into the south—west. cloud and outbreaks of rain looking north—east across the northern isles are behind that this drier slice of weather and perhaps one or two showers but then wet weather picking into the south—west, parts of wales and northern ireland with temperatures dying on where they were on sunday. a maximum of around 20 degrees. as we move into tuesday, low pressure still dominates in this area of low pressure contains the remnants of hurricane alberto, that cold front bringing heavy rain as we move into the start of tuesday. could be a tricky rush hour for the east and it will work north and east through the day. something brighter feeding will work north and east through the

day. something brighterfeeding and perhaps for parts of england and wales but behind it showers and a brief dry interlude for northern ireland. temperatures in the mid to high teens. enter midway, an u nsettled high teens. enter midway, an unsettled picture with further spells of heavy rain and some strong winds to come as well. here is how the pressure chart looks into wednesday. you can still see these weather fronts working in off the atla ntic weather fronts working in off the atlantic and the isobars are still tight together. still some blustery conditions to be seen. through wednesday, outbreaks of rain, some heavy, as it moves across central and eastern parts of england and we could see something brighter feeding in to western areas later in the day. temperatures in the mid to high teens. 15—17 in the north and 17—19 in the south. it was the second half of the week, low pressure remains dominantand of the week, low pressure remains dominant and you can see those isobars still close together so further breezy weather, spells of

rain and showers. heaviest towards the north and west. the following weekend, the jet stream sets to the south of the uk and that lies that area of low pressure to gradually edge further towards the east. we will see an area of high pressure brought about by what is currently tropical storm gerry edging from the west. and we could see and northerly flow. that flow develops, there is uncertainty on the detail at the moment but we could see a real dip in temperatures for the last few days of september. and the start of october. a real change to come after the warmth of saturday. bye—bye.

this is bbc news i‘m rachel. the headlines at 10pm. jeremy corbyn has quashed an attempt to oust tom watson as the deputy leader of the labour party, a row which has overshadowed the start of the party‘s conference in brighton. i‘m particularly disappointed with john, the boss of momentum, because i think he is notjust undermined me, ithink i think he is notjust undermined me, i think is undermined jeremy, i think is undermined the party, and frankly, i think is undermined the momentum. iran reacts defiantly — in response to the us sending troops and missile defence systems to saudi arabia and the uae — after last week‘s attack on saudi oilfacilities. teenage climate activist greta thunberg arrives to cheering crowds at a youth summit on climate change in new york — ahead of the un general assembly next week. in football, kevin de bruyne helps

man city score a massive eight goals